U.S. patent application number 12/768859 was filed with the patent office on 2011-05-12 for method and system for manufacturing microstructure in photosensitive glass substrate.
This patent application is currently assigned to INDUSTRIAL TECHNOLOGY RESEARCH INSTITUTE. Invention is credited to Jeng-Shyong Chen, Chung-Wei Cheng, Chih-Wei CHIEN, Ping-Xiang Li.
Application Number | 20110108525 12/768859 |
Document ID | / |
Family ID | 43973376 |
Filed Date | 2011-05-12 |
United States Patent
Application |
20110108525 |
Kind Code |
A1 |
CHIEN; Chih-Wei ; et
al. |
May 12, 2011 |
METHOD AND SYSTEM FOR MANUFACTURING MICROSTRUCTURE IN
PHOTOSENSITIVE GLASS SUBSTRATE
Abstract
The present invention provides a method and system for
manufacturing a microstructure in a photosensitive glass substrate,
which include the steps of generating first femtosecond laser
pulses by a femtosecond laser source and focusing the first
femtosecond laser pulses on a surface or an interior of the
photosensitive glass substrate by a focus lens to define a modified
region; generating second femtosecond laser pulses by the
femtosecond laser source, adjusting a frequency of the second
femtosecond laser pulses to be higher than that of the first
femtosecond laser pulses by a frequency adjustment unit and an
energy adjustment unit; focusing the adjusted second femtosecond
laser pulses on the modified region of the photosensitive glass
substrate to crystallize a substance of the modified region; and,
after crystallization, etching off the crystallized region to
obtain the microstructure in the photosensitive glass
substrate.
Inventors: |
CHIEN; Chih-Wei; (Hsinchu,
TW) ; Cheng; Chung-Wei; (Hsinchu, TW) ; Li;
Ping-Xiang; (Hsinchu, TW) ; Chen; Jeng-Shyong;
(Hsinchu, TW) |
Assignee: |
INDUSTRIAL TECHNOLOGY RESEARCH
INSTITUTE
Hsinchu
TW
|
Family ID: |
43973376 |
Appl. No.: |
12/768859 |
Filed: |
April 28, 2010 |
Current U.S.
Class: |
216/87 ;
156/345.1 |
Current CPC
Class: |
C03C 15/00 20130101;
C30B 29/34 20130101; C30B 1/023 20130101; C03C 23/0025
20130101 |
Class at
Publication: |
216/87 ;
156/345.1 |
International
Class: |
B44C 1/22 20060101
B44C001/22; C23F 1/08 20060101 C23F001/08 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 11, 2009 |
TW |
098138200 |
Claims
1. A method for manufacturing a microstructure in a photosensitive
glass substrate, comprising: focusing first femtosecond laser
pulses on a surface or the interior of the photosensitive glass
substrate to define a modified region; focusing second femtosecond
laser pulses having a frequency higher than that of the first
femtosecond laser pulses on the modified region to crystallize a
substance of the modified region; and after the step of focusing
second femtosecond laser pulses, etching off the crystallized
region to obtain the microstructure.
2. The method of claim 1, wherein the first femtosecond laser
pulses and the second femtosecond laser pulses are generated by a
femtosecond laser source, and the pulse widths of the first
femtosecond laser pulses and the second femtosecond laser pulses
are smaller than or equivalent to 500 fs.
3. The method of claim 1, further comprising: adjusting the energy
of the first femtosecond laser pulses before the step of focusing
the first femtosecond laser pulses to allow the laser intensity of
the first femtosecond laser pulses focused on the photosensitive
glass substrate to rang between 0.2 and 2 J/cm.sup.2.
4. The method of claim 1, wherein the first femtosecond laser
pulses and the second femtosecond laser pulses are focused by a
lens.
5. The method of claim 1, wherein the frequency of the second
femtosecond laser pulses conforms to the following formula:
f.gtoreq.D.sub.t/d.sup.2, wherein f is the frequency of the second
femtosecond laser pulses, D.sub.t is a thermal diffusion
coefficient of the photosensitive glass substrate and d is a
diameter of a laser spot of the second femtosecond laser pulses
focused on the photosensitive glass substrate.
6. The method of claim 5, wherein the laser intensity of the
focused second femtosecond laser pulses on the photosensitive glass
substrate ranges between 0.01 and 0.1 J/cm.sup.2.
7. The method of claim 1, wherein the photosensitive glass
substrate contains silicon dioxide and metal oxides of lithium,
silver and cerium.
8. The method of claim 7, wherein the step of focusing the first
femtosecond laser pulses allows an atom type silver to be formed in
the modified region.
9. The method of claim 7, wherein the step of focusing the second
femtosecond laser pulses allows a Li.sub.2SiO.sub.3 crystal to be
formed in the modified region.
10. The method of claim 9, wherein the frequency of the second
femtosecond laser pulses conforms to the following formula:
f.gtoreq.D.sub.t/d.sup.2 wherein f is the frequency of the second
femtosecond laser pulses, D.sub.t is a thermal diffusion
coefficient of the photosensitive glass substrate and d is a
diameter of a laser spot of the second femtosecond laser pulses
focused on the photosensitive glass substrate.
11. The method of claim 1, wherein the step of etching off the
crystallized region is performed by a hydrofluoric acid
solution.
12. The method of claim 1, wherein the first femtosecond laser
pulses have a frequency of 1 kHz and energy of 0.2 mW and are
focused by a 10.times. objective lens and the focused first
femtosecond laser pulses scan the surface of the photosensitive
glass substrate with a scanning speed of 0.05 mm/s.
13. The method of claim 1, wherein the second femtosecond laser
pulses have a frequency of 80 MHz and energy of 300 mW and is
focused by a 50.times. objective lens, and the focused second
femtosecond laser pulses scan the modified region with a scanning
speed of 0.5 mm/s.
14. The method of claim 1, wherein the first femtosecond laser
pulses have a frequency of 1 kHz and energy of 0.255 mW and are
focused by a 10.times. objective lens, and the focused first
femtosecond laser pulses scan the interior of the photosensitive
glass substrate with a scanning speed less than 0.5 mm/s.
15. The method of claim 14, wherein the second femtosecond laser
pulses have a frequency of 80 MHz and energy of 300 mW and are
focused by a 50.times. objective lens, and the focused second
femtosecond laser pulses scan the modified region with a scanning
speed of 0.5 mm/s.
16. A system for manufacturing a microstructure in a photosensitive
glass substrate, comprising a carrier; a femtosecond laser source
for generating femtosecond laser pulses; a frequency adjustment
unit configured along a transmission path of the femtosecond laser
pulses to adjust frequency of the femtosecond laser pulses; an
energy adjustment unit configured along the transmission path of
the femtosecond laser pulses to control energy of the femtosecond
laser pulses; and a focus lens for focusing the femtosecond laser
pulses with adjusted frequency and energy on a surface or the
interior of the photosensitive glass substrate loaded on the
carrier.
17. The system of claim 16, further comprising a movement control
mechanism connected to the carrier to move the carrier relative to
the femtosecond laser pulses.
18. The system of claim 16, further comprising a movement control
mechanism connected to the femtosecond laser source to allow the
femtosecond laser pulses to move relative to the carrier, thereby
forming a modified pattern and a crystallized pattern.
19. The system of claim 16, further comprising a reflective mirror
for changing the direction of the light path of the femtosecond
laser pulses.
20. The system of claim 16, wherein the femtosecond laser source,
the frequency adjustment unit and the energy adjustment unit are
fastened to each other.
Description
TECHNICAL FIELD
[0001] The present invention relates to the manufacture of a
microstructure in a photosensitive glass substrate, and more
particularly to a method and a system for manufacturing a
microstructure in a photosensitive glass substrate by a femtosecond
laser.
BACKGROUND
[0002] Photosensitive glass is substance with high transparency,
high hardness, high chemical resistance and high heat resistance.
Because the glass is doped with specific metal elements, the
absorbance thereof to radiation with a wavelength between 250 to
350 nm is high. Therefore, the photosensitive glass is usually used
in the manufacture of biochips and glass inserts.
[0003] To manufacture microstructures on surfaces of the
photosensitive glass substrates, the typical process includes the
following steps: modifying specific regions of the photosensitive
glass substrates by exposure and development processes; tempering
the entire photosensitive glass substrates in a heating furnace to
produce crystals in the modified regions; and etching off the
crystal-containing modified regions (also called crystallized
regions in the present application) by acid solutions to obtain
microstructures of photosensitive glass substrate (due to the
phenomenon that the speed of the crystallized regions responsive to
the acid solutions is 20-40 times faster than that of the
non-crystallized regions). However, common exposure and development
processes can only form microstructures on the surfaces of the
photosensitive glass substrates; and, when performing the temper
treatment in the heating furnace, unnecessary deformation happens
in the unmodified regions of the photosensitive glass substrates
due to heating. In addition, it takes several hours to perform the
temper treatment in the heating furnace. That is inconvenient in
use and is time-consuming.
[0004] U.S. Pat. Nos. 5,314,522, 7,029,806, 6,692,885, 7,018,259,
7,132,054, 5,374,291 and 7,041,229 disclose that the exposure
process is performed with a photomask under a UV radiation having a
wavelength of about 300 nm. However, the method disclosed in the
above patents still needs the temper treatment in the heating
furnace. As such, the above-mentioned problems can not be
overcome.
[0005] U.S. Pat. No. 7,033,519 discloses a method containing the
following steps: modifying the surfaces and the interior of the
photosensitive dielectric substances by a femtosecond laser;
tempering in a heating furnace; and etching. The method disclosed
in that patent reduces the time for modification or exposure and
improves precision of structures, but the step of tempering in the
heating furnace still causes the deformation of the unmodified
regions, such that the yield of the process cannot be
increased.
[0006] Hence, there is an urgent demand to avoid the deformation of
the unmodified regions caused by the temper treatment and to
improve the alignment precision.
SUMMARY
[0007] In view of the shortcomings of the above prior art, the
present invention provides a method for manufacturing a
microstructure in a photosensitive glass substrate, wherein the
method comprises: focusing first femtosecond laser pulses on a
surface or the interior of the photosensitive glass substrate to
define a modified region; focusing second femtosecond laser pulses,
which have a frequency higher than that of the first femtosecond
laser pulses, on the modified region to crystallize a substance in
the modified region; and, after the step of focusing second
femtosecond laser pulses, etching off the crystallized region to
obtain the microstructure.
[0008] In this method, preferably, the first femtosecond laser
pulses and the second femtosecond laser pulses of the present
invention are generated by a femtosecond laser source, wherein
pulse widths of the first femtosecond laser pulses and the second
femtosecond laser pulses are smaller than or equivalent to 500
fs.
[0009] In one embodiment, the frequency of the second femtosecond
laser pulses conforms to the following formula:
f.gtoreq.D.sub.t/d.sup.2, wherein f is the frequency of the second
femtosecond laser pulses, D.sub.t is a thermal diffusion
coefficient of the photosensitive glass substrate and d is a
diameter of a laser spot of the second femtosecond laser pulses
focused on the photosensitive glass substrate.
[0010] In addition, the present invention provides a system for
manufacturing a microstructure in a photosensitive glass substrate,
wherein the system comprises: a carrier for loading the
photosensitive glass substrate; a femtosecond laser source for
generating femtosecond laser pulses; a frequency adjustment unit
configured along a transmission path of the femtosecond laser
pulses to adjust the frequency of the femtosecond laser pulses; an
energy adjustment unit configured along the transmission path of
the femtosecond laser pulses to adjust energy of the femtosecond
laser pulses; and a focus lens for focusing the femtosecond laser
pulses with adjusted frequency and energy on a surface or the
interior of the photosensitive glass substrate loaded on the
carrier.
[0011] In one embodiment, the system of the present invention
further includes a movement control mechanism, which is connected
to the carrier to move the carrier relative to the femtosecond
laser pulses.
[0012] In another embodiment, the movement control mechanism of the
present invention is connected to the femtosecond laser source to
allow the femtosecond laser pulses moving relative to the carrier
to form a modified pattern and a crystallized pattern.
[0013] Compared with the prior art, second femtosecond laser pulses
of the present invention that have a frequency higher than that of
the femtosecond laser pulses used to form the modified region is
focused on the modified region to perform a local tempering
treatment, such that the unmodified region of the present invention
does not deform due to the heating. Moreover, an ideal
microstructure can be obtained after etching because the focused
femtosecond laser pulses have high alignment precision and the
non-focused region of the photosensitive glass substrate is not
treated and is not crystallized. Therefore, the present invention
has the advantages of reducing the steps and time in the process
and obtaining the microstructure with high precision.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The patent or application file contains at least one drawing
executed in color. Copies of this patent or patent application
publication with color drawing(s) will be provided by the Office
upon request and payment of the necessary fee.
[0015] FIG. 1A is a schematic diagram showing a system for
manufacturing a microstructure in a photosensitive glass substrate
according to an embodiment of the present invention;
[0016] FIG. 1B is a schematic diagram showing a system for
manufacturing a microstructure in a photosensitive glass substrate
according to another embodiment of in the present invention;
[0017] FIG. 2A is a schematic diagram showing a system for
manufacturing a microstructure in a photosensitive glass substrate
that has a movement control mechanism according to a further
embodiment of the present invention;
[0018] FIG. 2B is a schematic diagram showing a system for
manufacturing a microstructure in a photosensitive glass substrate
that has a movement control mechanism according to still another
embodiment of the present invention;
[0019] FIG. 3A shows a picture (from an optical microscope) of a
surface microstructure in a photosensitive glass substrate
manufactured according to an embodiment of the present
invention;
[0020] FIG. 3B shows a picture (from an optical microscope) of a
microstructure that is not manufactured under the conditions of the
present invention;
[0021] FIG. 4 shows a cross-section diagram of portions of a
photosensitive glass substrate being treated according to an
embodiment of the method of the present invention; and
[0022] FIGS. 5A and 5B show pictures (from an optical microscope)
of a blind via of the photosensitive glass substrates and the
micro-channel thereof in the present invention, wherein FIG. 5B
shows the thinnest part of about 5 .mu.m in the middle section of
the micro-channel.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] The following illustrative embodiments are provided to
illustrate the disclosure of the present invention. Those in the
art will be able understand other advantages and effects of the
present invention after reading the disclosure of this
specification.
[0024] The present invention relates to a method for manufacturing
a microstructure in a photosensitive glass substrate by a
femtosecond laser. In the present invention, the photosensitive
glass substrate can be modified and tempered by the same laser
source to obtain a crystallized pattern. In another aspect, the
subject to be treated by the present invention is a photosensitive
glass substrate. Typically, the photosensitive glass substrate
contains many metal elements such as lithium, silver and cerium, or
metal ions in the form of a metal oxide in addition to silicon
dioxide. One non-imitating example is used to illustrate the
components of the photosensitive glass substrate as follows. A
photosensitive glass substrate contains, based on the total weight
of the photosensitive glass substrate, 75 to 85 wt % of silicon
dioxide, 7 to 11 wt % of lithium oxide, 3 to 6 wt % of potassium
oxide, 3 to 6 wt % of aluminum oxide, 1 to 2 wt % of sodium oxide,
less than 2 wt % of zinc oxide, 0.2 to 0.4 wt % of antimony oxide
(Sb.sub.2O.sub.3), 0.05 to 0.15 wt % of silver oxide and 0.01 to
0.04 wt % of cerium oxide (CeO.sub.2). In this photosensitive glass
substrate, the doped cerium ions therein are used as a
photosensitizer and release electrons to silver ions after
absorbing the energy from femtosecond laser pulses, such that the
silver ions are transformed into silver atoms. It should be noted
that the energy of first femtosecond laser pulses of the present
invention used to modify the photosensitive glass substrate is
adjusted to a suitable extent, and then the first femtosecond laser
pulses are focused on the predetermined region, such as a surface
or the interior, of the photosensitive glass substrate by a focus
lens to define a modified region, such that the photosensitive
glass substrate receives a laser intensity ranging between 0.2 and
2 J/cm.sup.2 to transform the silver ions into silver atoms.
However, because the energy received by the regions that are out of
focus of the laser is insufficient, no reaction occurs in the
non-focused regions of the photosensitive glass substrate (i.e. no
silver atoms are formed). For example, when the interior of the
photosensitive glass substrate is modified, the surface thereof is
out of focus, and thus the surface will not be modified by the
first femtosecond laser pulses (i.e. no silver atoms will be
formed) and no crystals will not produced during tempering
treatment.
[0025] In the second step of the method of the present invention,
the second femtosecond laser pulses that have a frequency higher
than that of the first femtosecond laser pulses are focused on the
modified region of the photosensitive glass substrate, such that
the substance of the modified region is crystallized. In this step,
similarly, the same lens focuses the second femtosecond laser
pulses and the focused pulses are allowed to scan along the trace
of the first femtosecond laser pulses for modification. When the
frequency (f) of the second femtosecond laser pulses is adjusted to
be higher than that of the first femtosecond laser pulses, the
thermal cumulative effect generated by femtosecond laser pulses
heats the scanned modified region to produce crystals. In the
present application, the frequency of the second femtosecond laser
pulses is higher than that of the first femtosecond laser pulses,
and preferably, the frequency of the second femtosecond laser
pulses conforms to the following formula:
[0026] f.gtoreq.D.sub.t/d.sup.2, wherein f is the frequency of the
second femtosecond laser pulses, D.sub.t is a thermal diffusion
coefficient of the photosensitive glass substrate and d is a
diameter of a laser spot of the second femtosecond laser pulses
focused on the photosensitive glass substrate. D.sub.t can be
obtained from the formula: D.sub.t=.kappa./.rho.Cp, wherein .kappa.
is a thermal conduction coefficient (W/mK) of a photosensitive
glass substrate; .rho. is the density (kg/m3) of a photosensitive
glass substrate; and Cp is specific heat (J/(KgK) of a
photosensitive glass substrate).
[0027] For example, when the frequency of the second femtosecond
laser pulses is higher than the value obtained from the formula
(D.sub.t/d.sup.2), it will be the case that silver atoms in the
scanned modified region aggregate to be of a silver atomic group
(Ag.sub.x) and that Li.sub.2SiO.sub.3 crystals are produced around
the silver atomic group. In the step of thermal treatment to
produce crystals (i.e. the step of focusing the second femtosecond
laser pulses), when d is 5 .mu.m, the frequency of the second
femtosecond laser pulses is usually higher than 2.59 MHz. Energy of
the second femtosecond laser pulses is adjusted to allow a laser
intensity on the photosensitive glass substrate to range between
0.01 and 0.2 J/cm.sup.2.
[0028] Because the speed of the crystallized region responsive to
an acid solution is 20-40 times faster than that of the unmodified
region, which is not modified and tempered, in the last step, the
crystallized region is etched off to obtain the microstructure of
the present invention. In an embodiment, a hydrofluoric acid
solution is used in etching and ultrasonic vibration is used to
accelerate the etching.
[0029] In addition, the present invention also provides a system
for manufacturing a microstructure in a photosensitive glass
substrate. As shown in FIG. 1A, the system includes: a carrier 101
for loading a photosensitive glass substrate 100; a femtosecond
laser source 103 for generating femtosecond laser pulses 105; and a
frequency adjustment unit 107, which is configured along a
transmission path of the femtosecond laser pulses 105 to adjust the
frequency of the femtosecond laser pulses 105; an energy adjustment
unit 109, which is set up along the transmission path of the
femtosecond laser pulses to adjust the energy of the femtosecond
laser pulses 105; and a focus lens 111 for focusing the femtosecond
laser pulses 105 with adjusted frequency and energy onto a surface
or the interior of the photosensitive glass substrate 100. It
should be noted that the setup of the frequency adjustment unit 107
and the energy regulation unit 109 in the present invention are not
limited in order, such that it is also possible to adjust the
energy first and then adjust the frequency.
[0030] In another embodiment shown in FIG. 1B, the system for
manufacturing a microstructure in a photosensitive glass substrate
further includes a reflective mirror 113 for changing a direction
of a light path of the femtosecond laser pulses 105. As the example
shown in FIG. 1B, the direction of the light path of the
femtosecond laser pulses 105 changes about 90.degree..
[0031] Referring to another embodiment shown in FIG. 2A, a system
of the present invention further includes a movement control
mechanism 115, which is connected to the carrier 101 to move the
carrier 101 relative to the femtosecond laser pulses 105 and
facilitates the formation of the microstructure. Since there are
many examples of the movement control mechanism 115 known to those
skilled in the art, it is not further described herein.
[0032] Further referring to another embodiment shown in FIG. 2B, a
system of the present invention further includes a movement control
mechanism 115', which is connected to the femtosecond laser source
103 to allow the femtosecond laser pulses 105 to move relative to
the carrier 101 to form a modified pattern and a crystallized
pattern. In practice, as shown in FIG. 2B, the femtosecond laser
source 103, the frequency adjustment unit 107, the energy
adjustment unit 109 and the focus lens 111 can be installed in a
casing 117, and the movement control mechanism 115' is connected to
the casing and/or the femtosecond laser source 103 to control the
movement of the femtosecond laser pulses 105 on the photosensitive
glass substrate 100. Certainly, the femtosecond laser source 103,
the frequency adjustment unit 107 and the energy adjustment unit
109 can be simply fastened to each other by connectors as long as
the frequency adjustment unit 107 and the energy adjustment unit
109 are configured along the transmission path of the femtosecond
laser pulses 105.
Example 1
Manufacture of Surface Microstructure in Photosensitive Glass
Substrate
[0033] In this example, the femtosecond laser pulses with a
frequency of 1 kHz and energy of 0.2 mW were focused on the surface
of a photosensitive glass substrate by a 10.times. objective lens
to modify the surface with a scanning speed of 0.05 mm/s to define
a modified region. Then, the second femtosecond laser pulses with a
frequency of 80 MHz and energy of 300 mW were focused on the
surface of the photosensitive glass substrate by a 50.times.
objective lens and the second focused femtosecond laser pulses
scanned the modified region of the photosensitive glass substrate
with a speed of 0.5 mm/s for the tempering treatment. Finally, the
crystallized region was removed by 8% of hydrofluoric acid
accompanied with ultrasonic vibration for 15 minutes.
[0034] As shown in FIG. 3A, the position circled by the dotted line
A shows that a groove is formed by the method of Example 1.
However, as shown in FIG. 3B, if tempering is performed by
femtosecond laser pulses with a frequency less than the value
obtained from D.sub.t/d.sup.2, the groove is not be formed.
Example 2
Manufacture of Blind Via of Photosensitive Glass Substrate
[0035] In this example, femtosecond laser pulses with a frequency
of 1 kHz and energy of 0.255 mW were focused on the interior of a
photosensitive glass substrate by a 10.times. objective lens for
modification, wherein, as shown in FIG. 4, in order to form
modified regions of pits 402 at two positions of the surface of the
photosensitive glass substrate 400, the femtosecond laser pulses
scanned from the surface of the photosensitive glass substrate down
to a depth (D) of 0.2 mm at the predetermined two ends of a blind
via at a speed less than 0.5 mm/s, such as 0.05 mm/s. The
micro-channel 404 connected between the pits 402 of the
photosensitive glass substrate was scanned by a speed of 0.5 mm/s
to form a U-shaped modified region. Then, the femtosecond laser
pulses with a frequency of 80 MHz and energy of 330 mW were focused
on the interior of the photosensitive glass substrate by a
50.times. objective lens and scanned the modified region of the
photosensitive glass substrate with the above-mentioned speed for
the tempering treatment. Finally, the crystallized region was
removed by an 8% hydrofluoric acid solution accompanied with
ultrasonic vibration for 15 minutes.
[0036] As shown in FIG. 5A, after etching about 49 minutes, the
micro-channel of this example was formed. As shown in FIG. 5B, the
thinnest part in the middle section of the micro-channel is about 5
.mu.m.
[0037] Based on the above, it is known that a microstructure can be
rapidly manufactured on a surface or the interior of a
photosensitive glass substrate by the method and system of the
present invention. Further, the thinnest and most precise patterns
and micro-channels can be obtained under the conditions disclosed
in the present invention.
[0038] The foregoing descriptions of the detailed embodiments are
illustrated to disclose the principles and functions of the present
invention and are not intended to restrict the scope of the present
invention. It should be understood by those in the art that many
modifications and variations can be made according to the spirit
and principles in the disclosure of the present invention and yet
fall within the scope of the appended claims. The specification and
examples are considered as exemplary only, with the true scope of
the invention being indicated by the following claims.
* * * * *